Biofuel, including biodiesel and other biohydrocarbons is considered to be a promising alternative to fossil fuels. Biofuel may be produced from different types of cells and cell components. For example, biofuel may be produced from microalgal lipids. To achieve commercially viable biodiesel production from microalgae, high biomass and high lipid content are required. However, the conditions favouring high biomass productivity usually result in low lipid accumulation, and vice versa. Under stress conditions, as growth rate drops, microalgae tend to accumulate larger lipid content. Thus, the requirements of high biomass and high lipid content are inherently contradictory and entail diligent optimization of process conditions. To achieve this, it is essential to be able to monitor lipid accumulation.
Microalgae are essentially microscopic algae typically found in freshwater and marine systems, mostly unicellular and can exist individually or in groups. According to the species, their sizes differ in range from a few micrometers to a few hundred micrometers. They are capable of performing photosynthesis and produce just about half of the atmospheric oxygen and simultaneously consume carbon dioxide. Microalgae are found at the base of the food web, which highlights their importance on earth, and provide energy for all the trophic levels above them.
Microalgae are attaining increasing attention due to their wide range of applications in biology and biotechnology industries. The demands of microalgae as biodiesel are on a leap in the modern era due to the increasing demand for fuels and environmental safety. The main features that make the biofuels a smart alternative to fossil fuels are that they are renewable sources of energy, environment friendly and are economically significant. They possess high biomass productivity, speedy lipid accumulation and can survive in saline water. Biofuels are expected to take the place of fossil fuels in the future due to the demand for clean energy, economic potential and renewable nature.
Microalgae are rich sources of carbohydrates, lipids and proteins which make them important sources of feedstock. The presence of long chain fatty acids, proteins and carbohydrates makes them important as components of health food supplements as well as various pharmaceutical industries.
Oleaginous microalgae like the Chlorella, Nannochloropsis, Scenedesmus species are particularly important sources of biofuels as well as feedstock due to the high levels of proteins and polyunsaturated fatty acids. The biomolecule components can be enhanced by manipulating the various parameters by subjecting them to stress, both genetic and environmental (light, temperature, nutrient depletion like carbon or nitrogen, light intensity, salinity or harvesting procedure).
High biomass growth rate coupled with high nutrient content can be achieved simultaneously in a bioreactor. Engineering the growth medium, proper selection of the algal strains, use of genetic engineering and use of suitable extraction methods can optimize nutrient content. The studies involving continuous monitoring of the food, biofuel and other coproduct production requires continuous monitoring of the biochemical components.
Proteins make up a large portion of the cellular membrane and are important components of a number of enzymes that carry out the various cellular activities. Some microalgal species like Nannochloropsis sp., Dunaliela sp. and Chlorella sp. are able to accumulate 25-60% of lipids/dry weight. Biochemical methods have been used for the extraction of proteins, carbohydrates and lipids. Such methods involved use of strong alkali, acid and organic solvents. The cells have strong cell walls and the alkali treatment used for protein extraction lyses the cell walls. The ethanol precipitation helps the carbohydrates to be extracted completely. Several methods tried for lipid extraction turned out to be not entirely satisfactory as there was loss or incomplete extraction of lipids and some of them were time consuming.
A vast majority of the conventional techniques that are used to determine the biomolecule components (carbohydrates, lipids, proteins, nucleic acids, vitamins etc.) of microalgae in a culture for a bioreactor are labor intensive and time consuming. These procedures make use of various methods and reagents that are disparaging and hazardous to health as well as the environment.
The accurate, continuous and rapid detection of the amounts of carbohydrates, lipids and proteins in microalgal cells in a culture container of a bioreactor are extremely crucial and highly demanded in the field while engineering the microalgae for the production of distinctive type of biofuels.